Generally, electromagnetic actuators can generate a strong electromagnetic force with short strokes and are often used for mechanism portions of vacuum circuit breakers. However, in switches or disconnecting switches other than vacuum circuit breakers, electromagnetic actuators that are rotary driven and have long strokes are often used.
In connection with the number of positions where a mover stabilizes, there is a two-stable electromagnetic actuator in which a mover stops in two positions in synchronization with an operation of “ON” and “OFF” of a switch or a disconnecting switch. There is also a three-stable oscillating electromagnetic actuator in which a mover stops in three positions in synchronization with an operation of “ON”, “OFF”, and “ON” of a switch or a disconnecting switch having two stationary contacts and one moving contact.
For example, Patent Document 1 discloses a two-stable electromagnetic actuator. This actuator is suitable for a contact of a low voltage switch, because this actuator is two-stable actuator and has short strokes. Patent Document 2 discloses a three-stable electromagnetic actuator. This actuator has long strokes. However, because a path of a magnetic flux is mainly in a radial direction, the degree of contribution of the magnetic flux to a rotation driving force is low and thus efficiency thereof is low. Therefore, to apply this actuator to a contact of a large-electric power switch that requires a large driving force, this actuator needs to be made larger.
Patent Document 1: Japanese Patent Application Laid-open No. 2001-297912
Patent Document 2: Japanese Patent Application Laid-open No. S61-16504